Due to the upsurge of recent energy issues, an electric source with a higher energy density and with cleaner discharge has been demanded. A fuel cell is a generator with an energy density several fold those of existing batteries. A fuel cell has characteristic features of higher energy efficiency and little or no nitrogen oxides or sulfur oxides in discharged gases. Therefore, a fuel cell is an extremely effective device satisfying the demand as a next-generation electric source device.
The cell of a fuel cell comprises an anode-side catalyst (anode) and a cathode-side catalyst (cathode) on both the sides of the solid polymer electrolyte membrane as an electrolyte membrane. By alternately arranging a separator with an anode fluid path and a cathode fluid path formed thereon while these paths sit back to back and the cell, a cell unit is formed. By stacking a plurality of such cell units together, then, a cell stack is constructed. A fuel cell of such stack structure is equipped with a manifold for uniformly dividing a fuel to each of the cell units to uniformly feed the fuel in the cell stack, so as to feed the fuel from the manifold to each of the cell units.
When the fuel is fed non-uniformly to each of the cell units in the cell stack, the output from each of the cell units varies, leading to the reduction of the power generation, so that the output from the whole cell stack is affected by the output from a low-output cell unit. Therefore, it is demanded that such manifold should have a uniform division performance at a higher dimension for the fuel supply to each of the cell units in the cell stack.
In such circumstances, various techniques for uniformly feeding a fuel to each of the cell units in a cell stack have been proposed (the publication of JP-A-Hei 9-161828). For fuel supply, in the publication, the manifold is constructed with a second space for dispersion, which is arranged adjacent to the cell stack, and a first space where a hydrogen rich gas is fed. The hydrogen rich gas fed in the first space is transferred through a through hole to the second space, where the hydrogen rich gas is dispersed and fed to each of the cell units.
Because the hydrogen rich gas is dispersed in the second space, the variation in the feed volume between cell units close to the through hole and cell units remote from the through hole is reduced, so that the hydrogen rich gas can be fed uniformly to all the cell units in the cell stack.
Patent reference 1: JP-A-Hei 9-161828
Because the hydrogen rich gas is necessarily dispersed in the second space according to the conventional technique, it was required to make the ratio of the volume of the second space to the whole volume of the first space and the second space larger. Unless the distance from the through hole to the cell units is at a certain dimension, therefore, the feed volume of the hydrogen rich gas varies depending on the positional relation between the through hole and each of the cell units, so that the manifold should inevitably be made as a larger type so as to uniformly feed the hydrogen rich gas to each of the cell units.
In such circumstances, the invention has been achieved. It is an object of the invention to provide a fuel cell capable of uniformly feeding an anode fluid to each of the cell units even when the manifold is made as a small type.